This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 4 |
| 5 | 40 |
| 6 | 216 |
| 7 | 1603 |
| 8 | 13000 |
| 9 | 118872 |
| 10 | 1202880 |
| 11 | 13361403 |
| 12 | 161638764 |
| 13 | 2115684272 |
| 14 | 29792671832 |
| 15 | 449145795915 |
| 16 | 7217975402768 |
| 17 | 123180993414224 |
| 18 | 2224874726830656 |
| 19 | 42402252681323859 |
| 20 | 850380681002034900 |
| 21 | 17902407539998807896 |
| 22 | 394741856473979171608 |
| 23 | 9097740802923890621491 |